During the coming year we will concentrate on two proposed projects: 1) surface modification of ram testicular spermatozoa during storage in rete testis fluid (RTF) and cauda epididymal fluid (CEF) in vitro; and 2) within ram variation in the metabolic activity of ram testicular spermatozoa. a) When testicular spermatozoa are stored in RTF or CEF in vitro they develop markedly different patterns of glucose degradation. These differences may be associated with changes in the sperm cell surface protein pattern. We will, therefore, study changes in surface protein pattern of testicular spermatozoa during storage in these fluids using selective surface labeling and two-dimensional gel electrophoresis. b) There are 2- to 5-fold differences in the respiration rate and glycolytic activity between batches of unwashed testicular spermatozoa collected under identical conditions from the same ram. These changes may reflect differences in the composition of the fluid or they may be inherent in the spermatozoa. We will attempt to identify the factor(s) that cause these marked changes in spermatozoal activity between samples. This will be accomplished by comparing batches of washed spermatozoa in synthetic medium or by relating differences in metabolic activity to changes in the composition of the fluid.